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Design infrastructure as code like terraform

PremiumCloud infrastructureMedium

  • Terraform
  • State locking
  • Plan and apply

Quick answer

This cloud infrastructure interview question asks you to design infrastructure as code like terraform. Aim for a design that runs reliably and securely in the cloud at a sensible cost, then explain the services, regions, deployment and trade-offs. Interviewers want to see how you balance reliability, security and cost.

The problem

Design infrastructure as code like Terraform, plus the service that runs it for a whole company: engineers describe cloud resources in config files, the tool shows a plan and then applies it. The hard parts are keeping the state file correct, stopping two applies from racing, and catching drift.

The tool reads config, builds a dependency graph (a subnet needs its network first), compares desired config with recorded state refreshed against the real cloud, and shows a plan of creates, updates, replacements and deletes. Apply carries out the plan through provider plugins that call cloud APIs.

What must the system do?

  • Plan: For a workspace, show exactly which resources will be created, updated in place, replaced or destroyed, before anything changes.
  • Apply: Execute an approved plan in dependency order, in parallel where the graph allows, and record each result in state.
4 more requirementsUnlock to see all

How well must it do it?

  • State correctness: State is never lost, corrupted or written by two applies at once; every version is kept for 90 days.
  • Apply what was reviewed: An apply runs only the reviewed plan; if state changed since that plan, the apply refuses.
3 more requirementsUnlock to see all

What scale should you design for?

Use these numbers in your estimates.

The scale numbers unlock with this questionUnlock

Key concepts

  • Terraform
  • State locking
  • Plan and apply
  • Dependency graph
  • Drift detection
  • Remote state

How you’ll practise

6 short steps · save and come back any time
  1. Requirements
  2. Environments and topology
  3. Deployment pipeline
  4. Reliability and disaster recovery
  5. Observability and cost
  6. Wrap-up

Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.

What do interviewers look for?

In any cloud infrastructure design round.

  • Clarifies availability, security and cost targets
  • Chooses managed services with reasons
  • Plans regions, zones and failover
  • Covers identity, secrets and network boundaries
  • Explains deployment, rollback and observability
  • Keeps an eye on cost as usage grows

Questions people ask about this interview question

Which design type is this question?
It is a cloud infrastructure question. You design infrastructure as code like terraform and explain your choices the way you would in an interview.
Is this question asked at entry level?
It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
What should I cover first?
Start with the workloads, the availability target and the security and cost limits. Agree on scope with the interviewer before you design anything.
Can I practise it for free?
It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.

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Updated · Written by the SevyDevy team

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